The present invention relates to receiving and forming a selected number of individual sheet materials into a stack and discharging the formed stack.
Sheet materials such as corrugated paper used for box construction, are typically die-cut, printed, perforated or otherwise treated by a finishing machine. The flat blanks may be folded with joints secured by glue, while still in substantially flat configurations for later assembly. It is desirable to accumulate the relatively flat folded blanks in stacks that may be bound with straps or otherwise secured for shipment or storage until such time that a need arises for the blanks to be formed into boxes.
Forming rails and glue application heads are typically used downstream of the finishing machine to form the sheet material into desired configurations as they move along. A typical configuration is a partially folded box, the folding process for which is exemplified in FIG. 1 of the drawings.
In existing technology, the boxes are counted and accumulated in bundles by a counter-ejector machine. This is an area where difficulty is experienced, since the boxes being fed along a plane, in end-to-end relation often have a tendency to re-open at the glue lines (see FIG. 1) as they leave the folding rails. If a glue line re-opens, the loose flaps can cause frustrating and costly down-time while the single box blank is pulled from the counter-ejector.
Finishing machines, folding rails and glue applicators can be operated at fairly high speeds (in the area of 1000 feet per minute output). Stacking machinery, on the other hand is typically unable to operate sufficiently fast to stack the blanks at a similar rate. It therefore becomes desirable to provide a counter-ejector that will accumulate and stack sheets at an acceptably fast rate to avoid or minimize slowing or periodic stopping of the upstream machinery. An attempt has been made to increase the effective sheet handling speed by shingling sheets in a counter-ejector just prior to formation of the sheet stacks. The intent was to overlap and feed the sheets in a stream to a stacking station. However, control of the individual sheets was somewhat compromised and periodic jams could occur.
A problem also recognized with existing forms of counter-ejectors is that numerous controls, timing, and individual adjustments were required each time a stack of a different height or sheets of different dimension were to be stacked. Such complexities can lead to increased chances for error and increased maintenance and repair. A need has therefore been realized for simplification of counter-ejector construction.
Another problem area with counter-ejectors occurs in the stacking area where the sheets are fed into a stacking magazine. Sheets must transition from a substantially horizontal path of travel at a selected feed rate, stop abruptly, and change direction from the substantially horizontal feed path to a substantially vertical movement order to accumulate in a stack. Sheets are typically fed substantially horizontally with narrow edges facing the direction of travel and the large surface areas oriented substantially parallel to the horizontal path. Since the large surface areas of the sheets must become substantially perpendicular to the new path of movement during stacking, air resistance becomes a concern. The sheets, in other words, want to xe2x80x9cparachutexe2x80x9d in the stacking magazine.
An attempted solution to the air resistance problem has been to mechanically alter the path of movement at the discharge into the stacking magazine. While this allows some mechanical control to remain, the air resistance against the large sheet surface area remains during the transition from horizontal to vertical movement. Thus, a need also remains to provide control of the sheets during the horizontal to vertical transition, and to minimize the effects of air resistance as the sheets move vertically.
The present invention is intended to fill the above needs, as may be understood from the following description.